Method and equipment for continuously spinning and stretching synthetic filaments

ABSTRACT

A method and apparatus for continuously carrying out spinning and stretching operations on extruded synthetic filaments, wherein, between a conventional spinning apparatus and a conventional stretching apparatus for continuous treatment of the filaments, a bending and stretching action is imparted to the filaments by means of stationary bending means adapted to exert a predetermined frictional resistance on the running filaments.

United States Patent 1 Parmeggiani et a1.

METHOD AND EQUIPMENT FOR CONTINUO USLY SPINNING AND STRETCHING SYNTHETIC FILAMENTS Inventors: Paolo? 1 I Domenico Niclta;

Bruno D all Of Milan, ltaly Snia Viscose Societa Nazionale Industra Appllcazioni Viscosa, Milan, Italy Filed: Dec. 1, 1970 Appl. No.: 93,973

Assignee:

Foreign Application Priority Data Dec. 4, 1969 Italy 2535 A/69 References Cited UNITED STATES PATENTS 9/1958 Sharp 264/210 F 3/ 1959 Cuculo 264/210 F 7/1963 Haynes 28/1 [11] 3,752,457 Aug. 14, 1973 3,221,088 11/1965 Martin 264/210 F 3,259,681 7/1966 Bull et a]. 264/210 F 3,338,992 3/1967 Kinney 264/210 F 3,433,008 3/ 1969 Gage 264/210 F 3,436,797 4/1969 Graf et 81. 264/210 F 3,458,890 8/1969 Neal 264/210 F 3,499,953 3/1970 Stanley. 264/210 F 3,511,905 5/1970 Martin 264/210 F 3,522,342 7/1970 Nungessov.... 264/210 F 3,551,550 12/1970 Bauer 264/210 F FOREIGN PATENTS OR APPLXCATIONS 37/7903 7/1962 Japan 264/210 Primary Examiner-Jay l-l. Woo Attorney-Wenderoth, Lind & Ponack [5 7] ABSTRACT 4 Claims, 3 Drawing Figures PAIENTED M16 14 B73 PAOLO PARMEGGIANI, DOMENICO NICITA and BRUNO D 'ALO 4 ZL MMX' A M Attorneya METHOD AND EQUIPMENT FOR CONTINUOUSLY SPINNING AND STRETCHING SYNTHETIC FILAMENTS BACKGROUND This invention relates to the production of synthetic yarns, comprised in particular of polyesters and similar compounds and consisting of continuous filaments obtained by extrusion through a spinneret and then submitted separately or preferably submitted in the form of a plurality of parallely arranged filaments to a stretching process that is carried out by heating the filaments to a temperature adapted to allow the same to be stretched and simultaneously to allow molecular orientation and parallelization phenomena, typical for such synthetic products.

The production of such filaments and yarns is well known in the art and therefore a previous detailed description thereof is not essential for a better understanding of the background of this invention. It will be therefore sufficient to recall that such continuous filaments and yarns that are utilized in textile fields or for equivalent purposes are made by extruding a polymerized material into filaments stretch through the holes'of a suitable spinneret fitted at the outlet end of an extruder. The thus extruded filaments under their own weight during the gradual decrease in their plasticity while being submitted to desired cooling and conditioning processes, and are wound on suitable winders to be then submitted to a proper stretching process.

Owing to production requirements and conveniences, the taking-up operation of the filaments is usually performed at very high linear speeds, e.g., 800-1000 m/min., and the material which is gradually converted from its extruded plastic condition into cooled solid filaments, undergoes a small tension only (so called post-spinneret stretch") which is usually about 0.5 g/den.

The filaments thus obtained, wound and stored under suitable atmospheric conditions ("stockage) are then submitted to a desired stretching process with an elongation ratio which is usually, for polyester filaments, of the order of 1:3.8 l:4.4. The stretching process is performed by means of specific elements which substantially comprise a pair of suitably heated rotary stretching devices (called godets"), between which the filaments are highly stretched, usually in the range of 2.5 3 g/den., the upstream device being adapted to exert a required counter-stretching force. Owing to technological requirements and conveniences, the linear speed of the thus stretched filaments does not exceed an upper limit in the range of 800-1000 m/min. and therefore the filament inlet speed into the stretching device should not exceed a value in the range of 200-250 m/min.

The above condition is one of the reasons and perhaps the most important onewhich prevent the filaments from being submitted to a proper stretching process immediately after the post-spinneret stretch. In fact, the filaments come out from the primary" spinning system (this term defining the equipment wherein the starting material is extruded and converted into non stretched filaments) at a linear speed much higher than that conventionally required at the inlet of the stretching equipment.

On the other hand, the stretching operation could be performed at higher linear speeds, with outlet and taking-up speeds much higher than 3,000 m/min and therefore such high-speed stretching operation could be theoretically performed directly downstream of the primary spinning system. This could be accomplished by a secondary stretching system (wherein the extruded filament is converted into a stretched filament having a higher resistance and superior mechanical and physical properties) that operates directly downstream of the primary spinning system, with great production advantages. I

However, no favourable results were obtained by various attempts to combine such spinning and stretching systems. In fact, when the filaments are directly transferred from the spinning system to the stretching sys-. tem (which upstream godet represents therefore the post-spinneret stretching means, in place of conventional taking-up means), notwithstanding a postspinneret stretching operation and cooling, conditioning and enzyming processes carried out under the best conditions, easy and frequent filament breakage occurs, thereby causing difficulties which prevent the attainment of obviously desirable technical and economical results.

Different hypotheses might be advanced to explain these unsuccessful results in the experimentation of the system combinations. Generally speaking, the substantial difference between a separate carrying-out of primary spinning and stretching operations anda tensioning operation directly performed after the primary spinning, consists in that the first method includes the non stretched filaments being left in stock for a given time. Accordingly, during such time the spontaneous phenomena of molecular rearrangement or the like should occur. However, the applicants do not intend to,

make this invention dependent on the above assumption.

SUMMARY An object of this invention is to define and provide a method and means, respectively, by which the advantageous and desirable combination of primary spinning and stretching systems is made possible, together with important technical and economical advantages, under conditions such as to allow an effective and profitable production on an industrial scale, i.e., under conditions of high qualitative and quantitative performances, as well as with a high operating reliability of such means.

Accordingly, the solution of technical problems aiming to the removal of the causes (even when not totally known and defined) which apparently prevent a direct combination of a primary spinning system with a high speed stretching system, consists in providing means located directly upstream of the stretching system and adapted to carryout a physical treatment consisting in a limited and controlled stressing of the filaments.

In particular, such physical treatment consists of bending the filament around narrow surfaces shaped as circular segments and stationarily fitted in order to associate such bending action with a dragging action.

According to a preferred embodiment of this invention, the filaments are twice folded or bent in opposite directions causing the filaments to temporarily undergo (owing to the traveling resistance on said bending means), a slightly increased stretch, when compared with that imparted thereto by the post-spinneret operation.

Accordingly, the equipment of this invention essenbut not necessarilyin the form of small cylinders mounted to not rotate, located directly upstream of the upstream stretching means or godet" in the stretching system which exerts the pull required for the postspinneret stretch. The guide means is located and directed, with reference to the filament feeding and taking-up direction, in such a manner as to cause the filaments to bend in a required way and to exert the advantageous frictional resistance in order to obtain the above discussed slight incremental stretching action.

The small stationary cylinders preferably show not wholly smooth surfaces, wherein a satin-like finish or otherwise treatment is carried-out in such a manner as to provide the required slight frictional resistance. Moreover, preferably and in order to suitably built and operate the whole system, the pulling means or godet represents an upstream feeding means of a stretching section, in order to give the required counter-tension for the stretching action, as well as to ensure a filament heating action as required for the stretching operation.

Moreover, as economical and production requirements suggest and practically impose that the primary spinning and secondary stretching processes be simultaneously carried out on a plurality of filaments extruded through multiple spinnerets, the above described system according to this invention makes it possible to improve the parallelism and co-planarity of filaments. Therefore the filaments contact the godet under wholly uniform conditions. Such conditions are very improtant in high speed stretching operations owing to the very reduced contact time of filaments with the heated surfaces and to the necessity that the heat exchange should take place under strictly equal conditions for all filaments that run very close to each other.

The above and further more specific features of the invention, along with the demonstration of practicability of means adapted for the attainment of the novel and important industrial results and technical advantages will be better appreciated from the following detailed description with reference to the accompanying drawing.

DRAWING FIG. 1 is a diagrammatic view of a complete system operating according to this invention, wherein a stretching system is associated with a primary spinning equipment directly downstream thereof, for continuously producing polyester filaments, the devices and mechanisms which are already known being omitted.

FIGS. 2 and 3 are respectively more detailed axial and side views of a preferred embodiment of a device for a preparatory physical stretching treatment, the device preferably but not necessarily being associated with an upstream godet" structure of the stretching system equipment. The small cylinders of the device are shown in different positions in FIGS. 2 and 3.

PREFERRED EMBODIMENTS Referring firstly to FIG. 1, different elements are diagrammatically shown therein and a system for a primary spinning operation is defined by the components included in the bracket A. The equipment comprises an extruder with a multiple spinneret 12. The fialments l4 extruded from the spinneret are then stretched and hardened in an air quenching box 16. The filaments are then led across an elongated chamber 18 wherein a cooling operation is performed and any known desired conditioning operations are carried-out, whereafter they are led across a so called lantern" and finally (according to presently followed practices), to a taking-up device. Again according to present practices, the system also comprises suitable thread guides 22, means for suitably sizing the filaments and usually consisting of a pair ofenzyming rollers 24 and 26, and finally a spinning cup and taking-up means (not described or shown) that operate at a required linear speed in order to exert the required stretching for a filament postspinneret tensioning operation. Such tension is usually about 0.5 g/den. at the point X.

The bracket B defines a conventional stretching system with the exception of shown devices and means according to this invention which will be described below. This system comprises an upstream tensioning means in the form of a known suitably heated godet 28 and a downstream tensioning means in the form of one or more godets 30. These godets impart to the filaments the required oppositely directed tensions in order to have a tension value at the point Y in the range of 2.5 3 g/den. These godets are driven in such a manner as to have their filament contacting surfaces running at peripheral speeds corresponding to a required stretching ratio (of the order of 1:4 according to the nature and physical-chemical properties of the material, as well as to the intended applications thereof).

When a stretching system (e.g., the system B) is associated with a primary spinning system (as the system A) in such a manner as to have the filaments directly stretched at the outlet of system A, the upstream godet 28 shall obviously operate at a peripheral speed corresponding to the spinneret taking-up speed (which is advantageously in the range of 800-1000 m/min.) and thus the downstream godet 30 must operate at very high speeds, in the range of 3,200 4,000 m/min.

The reliability of the complex system resulting from an in-line association of system A and B, as well as the solution of previously examined technical problems are ensured, according to this invention, by an additional device, generally indicated by the latter Z and located upstream of the upstream godet" 28 (which latter is a known structure and thus will not be described in detail).

Device Z comprises a pair of small cylinders 36, 38 housed in a suitable supporting structure 32 which'is advantageously fastened to the frame 34 of godet 28. The cylinders are located in such a manner as to force the filaments to follow a path including a number of bends, in particular two oppositely directed bends as shown by dot and dash lines in FIG. 2, as well as to exert a frictional resistance on the running filaments in order to generate a tension slightly stronger than the post-spinneret tension, e.g., a tension in the range of 0.6 0.7 g/den. at the small filament length S between device Z and upstream godet 28.

Accordingly, small cylinders 36 and 38 have their surfaces treated in such a manner as to obtain the required frictional resistance. This surface treatment and resulting slight roughness can be easily established experimentally and obviously may vary according to a plurality of conditions, as e.g., the contact are lengths, the cylinder diameters, the actually applied postspinneret tension and the nature of the material.

In particular, as clearly shown in FIG. 2, the downstream located cylinder 38 shows a diameter different from that of upstream located cylinder 36. Such feature has proved to be advantageous. It may be assumed that the second bending around the downstream located cylinder results in a physical action on filaments together with an action exerted by bending around the upstream located cylinder.

It has been surprisingly ascertained that unforeseeable breakages and irregularities occurring in using a complex system as previously stated but without device Z, are wholly obviated by locating a pair of small cylinders having radii in the range of 2 to mm and arranged in such a manner as to bend the filaments around contact arcs corresponding to angles ranging from up to 130.

The diameter ratio ofupstream located cylinder 36 and downstream located cylinder 38 is preferably in the range of 2:1 to 1:2.

By way of example, in the continuous production of polyester filaments having a final count in the range of 20 to 1,200 den. and in particular of 50 to 840 den. and with the previously stated values of high speed stretching, good results were attained with an upstream located cylinder having a diameter of 8 mm and a downstream located cylinder having a diameter of 6 mm, as well as with a bend on the filaments, when running the said cylinders of 45 and respectively 1 10, as shown in FIG. 2. Minor changes in such values did not cause appreciable differences in the obtained results.

The device can be advantageously embodied as shown in FIG. 2 and 3. The housing 32 wherein the cylinders are fitted is secured to the frame 34 of godet 28 (or to any other stationary equipment component) by a pivot pin 40 in order to allow a device position adjustment for changing the length of the contact arcs and for obtaining an exerted physical action correspoinding to specific operating requirements.

The components of the device 2 have been defined as small cylinders and shown as such in the accompnaying drawings. However, such components are generally in the form of stationary bodies, formed with curved surfaces at least in the portions thereof that are designed to slidingly contact the filaments. Thus, the bodies might also show a not wholly circular section. On the other hand, the use of cylindric bodies is advantageous, even if their surfaces are not wholly utilized, due to obvious reasons of surface production and finishing. Moreover, in such cylindric bodies further surfaces are available for substituting worn or degraded surfaces, by simply turning the cylinders through a fraction of revolution.

Moreover it is to be understood that merely structural details not inherently featuring this invention may be changed and modified. Thus, e.g., the two cylinders 36 and 38 may be supported by two separate frame means relatively movable to allow different adjustments, in order to change the cylinder mutual spacing and the filament contact arc lengths. Obviously the cylinders may be replaceably fitted to allow a replacement or a substitution thereof with other cylinders having different diameters and/or surface features.

It is to be understood therefore that all such changes and modifications are included within the scope of this invention.

We claim:

1. In a melt spinning method for continuously spinning, stretching and winding-up synthetic filaments comprising extruding filaments from a spinneret under a reduced tension of about 0.5 glden; cooling and conditioning said filaments by passing said filaments through quenching and conditioning environments; mechanically stretching said filaments in a stretching zone by passing said filaments over an upstream godet rotating at a first speed and then passing said filaments over a downstream godet rotating at a secondspeed higher than said first speed; and windingingup the thus stretched filaments; the improvement comprising;

treating said filaments by an intermediate processing operation immediately prior to said step of mechanically stretching, said intermediate operation comprising bending said filaments in a first bending direction around a first circular arc, and then bending said filaments in a second opposite bending direction around a second circular arc, the path of said filaments during said bending steps having two circular arcs of angular amplitude between 20 and thereby increasing the tension by about 0.1-0.2 glden of and imparting a slight incremental stretch to said filaments between said second circular arc and said upstream godet.

2. An improved method according to claim 1, where in the radii of curvature of said first and second circular arcs are in the range of from 2-10 mm.

3. An improved method according to claim 2, wherein the ratio of said radii of curvature is in the range of from 1:2 to 2:1.

4. An improved method according to claim 1, wherein said filaments are of a polyester material, said step of mechanically stretching said filaments includes stretching said polyester filaments within the range of from 2.5-3.0 g/den., thereby providing an elongation ratio of from 1:3.8 to 124.4 to said polyester filaments. 

1. In a melt spinning method for continuously spinning, stretching and winding-up synthetic filaments comprising extruding filaments from a spinneret under a reduced tension of about 0.5 glden; cooling and conditioning said filaments by passing said filaments through quenching and conditioning environments; mechanically stretching said filaments in a stretching zone by passing said filaments over an upstream godet rotating at a first speed and then passing said filaments over a downstream godet rotating at a second speed higher than said first speed; and windingingup the thus stretched filaments; the improvement comprising; treating said filaments by an intermediate processing operation immediately prior to said step of mechanically stretching, said intermediate operation comprising bending said filaments in a first bending direction around a first circular arc, and then bending said filaments in a second opposite bending direction around a second circular arc, the path of said filaments during said bending steps having two circular arcs of angular amplitude between 20* and 130*, thereby increasing the tension by about 0.1-0.2 glden of and imparting a slight incremental stretch to said filaments between said second circular arc and said upstream godet.
 2. An improved method according to claim 1, where in the radii of curvature of said first and second circular arcs are in the range of from 2-10 mm.
 3. An improved method according to claim 2, whErein the ratio of said radii of curvature is in the range of from 1:2 to 2:1.
 4. An improved method according to claim 1, wherein said filaments are of a polyester material, said step of mechanically stretching said filaments includes stretching said polyester filaments within the range of from 2.5-3.0 g/den., thereby providing an elongation ratio of from 1:3.8 to 1:4.4 to said polyester filaments. 